Light-emitting diode (LED) is a semiconductor device which can directly convert the electric energy into the photoenergy, and has the characteristics of energy saving, environmental protection and long lifetime, etc., the rapid development and extensive use of LED will lead to a revolution in the field of lighting.
During the processing and use of the PCB substrate installed with LED, since the LED has light-emitting characteristics, the optical reflectivity of the surface of the resin layer should be as large as possible; and the copper-clad laminate for printed circuit board thereof undergoes a variety of heating processes during the manufacturing process of the chip LED; and when the chip LED is in use, the LED element itself will generate heat, and the LED will also generate heat stress when emitting light, therefore the white copper-clad laminate used for LED is required to have high heat resistance.
In addition to the general performance requirements of the conventional CCL are required, the white copper-clad laminate for LED is also required to have some special performances. The white copper-clad laminate for LED is not only required to have high initial state reflectivity, but also a characteristic of long-term retention of the reflectivity (including non-discoloration of the board under high-heat radiation, and non-discoloration of the board under the long-term ultraviolet irradiation), meanwhile it is also required to have high heat resistance, and high rigidity at high temperatures. To make the white CCL obtain high ultraviolet discoloration resistance and heat discoloration resistance, it mainly depends on the improvement or innovation in the performance of the various components in the resin composition to achieve this special performance.
Both organic groups and inorganic groups are contained in the structure of the organosilicone resin, such special composition and molecular structure make the silicone resin have both the characteristics of organics and the functions of inorganics. The organosilicone resin is a thermosetting resin, when it is under the thermal oxidation at high temperature, only the cleavage of the organic radicals on the side chains will occur, and they will be decomposed to escape their oxides, while the silicon-oxygen bond on the main chain is rarely destroyed, ultimately a polymer in a form of —O—Si—O— will be generated, the bond energy of their Si—O silicon-oxygen bond is 373 KJ/mol, thus their heat resistance is far superior to the general organic resins. The ultraviolet light is hardly absorbed by methylsiloxane, and siloxane containing PhSiO1.5 or Ph2SiO chain link only absorbs light with a wavelength of 280 nm or less, therefore the organosilicone resin has a very good weather resistance. In addition, the organosilicone resin has prominent weather resistance, which is beyond the reach of any kind of organic resins, even if it is irradiated under intense ultraviolet light, the silicone resin has very superior yellowing resistance.
Therefore, compared with the general resins, the organosilicone resin has unique properties such as excellent high and low temperature resistance, weather aging resistance, electrical insulation properties, ozone resistance, flame retardancy and hydrophobicity, etc.